This invention relates to a case for containing a circuit board with a light-receiving element disposed thereon and more particularly to a case which electromagnetically shields a light-receiving unit for a remote control apparatus.
An infrared ired light-receiving unit for a remote control video tape recorder or television set is generally disposed inside a case having a light-receiving window and operates when a light beam incident through this window is received by a light-receiving element on a circuit board. A conventional mechanism for securing a circuit board to such a case is shown in FIG. 5 wherein numeral 51 indicates a case housing with a plurality of positioning pieces 52 provided on its inner side walls. A circuit board 53 is inserted into the housing 51 as shown by the arrow and set against these positioning pieces 52. A base board 54 provided with a plurality of raised pieces 55 for supporting the circuit board 53 is set to the housing 51 to cover the bottom, surface of the circuit board 53. As shown in FIG. 6, the housing 51 has downwardly protruding parts 61a and the circuit board 53, as well as the base board 54, becomes fastened to the housing 51 with these protruding parts bent inwardly as shown in FIG. 7.
With a conventional case thus structured, however, it is difficult to position the circuit board 53 accurately and efficiently because positioning and securing of the circuit board are effected by means of both the case housing 51 and the base board 54. Unless both the case housing 51 and the base board 54 are firmly secured, the circuit board 53 may become disoriented and this can adversely affect the operation of a light-receiving element (not shown in FIGS. 5 and 6) attached to the circuit board 53. A light-receiving element shown at 56 in FIG. 7 is usually attached parallel to the circuit board 53 by bending its lead lines and a light-receiving window 57 is formed in the upper surface of the case housing 51. Since electronic components 58 such as LSI circuits and an output terminal 59 are mounted on the circuit board 53, it is generally required to provide a screening member (not shown) between the light-receiving element 56 and such electronic components 58 in order to electromagnetically shield these components against noise received through the light-receiving window 57.